''Cystiscus bougei'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of very small

sea snail Sea snails are slow-moving marine (ocean), marine gastropod Mollusca, molluscs, usually with visible external shells, such as whelk or abalone. They share the Taxonomic classification, taxonomic class Gastropoda with slugs, which are distinguishe ...

, a marine

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

mollusk Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The ...

micromollusk A micromollusc is a shelled mollusc which is extremely small, even at full adult size. The word is usually, but not exclusively, applied to marine molluscs, although in addition, numerous species of land snails and freshwater molluscs also ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Cystiscidae Cystiscidae is a taxonomic family of small sea snails, marine gastropod mollusks or micromollusks. Description The shell is minute to large, either white, uniformly colored, or patterned; the surface is smooth, sculptured, or axially costat ...

Description

''Cystiscus bougei'' is characterized by its minute size and smooth, glossy shell, typical of many species in the

family. The shell is usually oval to subcylindrical in shape, with a length ranging between 2 and 3 millimeters. Its small size classifies it as a

, meaning it is often not visible to the naked eye without magnification. The surface of the shell is generally smooth and polished, lacking any prominent ridges or spines that are commonly found in other types of

gastropods Gastropods (), commonly known as slugs and snails, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and from the land. Ther ...

. The color of the shell is typically pale, ranging from off-white to light brown, with some specimens exhibiting faint translucent or glass-like qualities. These muted colors allow the snail to blend into its sandy or muddy environment, helping it avoid predation. The aperture, or shell opening, is elongate and narrow, and it runs almost the entire length of the shell, a common feature in the genus '' Cystiscus''. The outer lip of the aperture is thickened, but lacks teeth, making it distinct from many other gastropods that have a more complex apertural structure. Internally, the shell structure is solid, offering protection despite its small size. The interior is glossy, reflecting the external smoothness, which helps reduce friction as the soft body of the snail retracts into the shell. Unlike many other marine snails, ''Cystiscus bougei'' does not possess an operculum, which is a hard plate used by some gastropods to seal the shell opening when retracted. The absence of an operculum in the family Cystiscidae suggests a different evolutionary adaptation for protection, where the small size and habitat selection (such as burrowing into sediment) play a primary defensive role. Though detailed anatomical descriptions of the soft body of ''Cystiscus bougei'' are scarce, it is presumed that the species possesses a typical gastropod body plan, with a muscular foot used for locomotion and a head with tentacles for sensory perception. The foot is also used for digging into the substrate, which assists the snail in burrowing to avoid predators. Its radula, the toothed feeding organ typical of most mollusks, is adapted for carnivorous feeding, likely allowing it to consume small prey such as microorganisms and other tiny invertebrates. Due to its small size, studying ''Cystiscus bougei'' requires specialized collecting methods. Researchers often collect specimens by sieving fine sediments from the sea floor, especially in areas like coral reefs or sandy environments where these snails thrive. Examination typically requires microscopes to accurately observe and measure the fine details of the shell structure. The delicate morphology of ''Cystiscus bougei'' underscores its adaptability to specific marine habitats. Its small, streamlined shell minimizes resistance when moving through sand or silt, and its smooth, glossy surface prevents particles from sticking to it. This micro-adaptation likely plays a role in its survival in dynamic, shallow-water environments where currents can shift fine sediments.

Distribution

''Cystiscus bougei'' typically inhabits Indo-Pacific waters, particularly around French Polynesia. This species is found in shallow to moderately deep waters, usually on soft substrates of sand or mud. Due to its small size and specialized habitat, it often goes unnoticed by the unaided eye, though it plays a significant role in marine ecosystems.

References

* Boyer F., 2003. The Cystiscidae (Caenogastropoda) from upper reef formations of New Caledonia. Iberus 21(1): 241–272. Gastropods described in 1917 bougei {{Cystiscidae-stub